“This Is Not America” declare the yellow neon letters transposed on to a glowing outline map of the United States. “This Is Not America’s Flag” reads a following pixellated sentence, as the image changes to the stars and stripes. The Chilean artist Alfredo Jaar’s billboard, named A Logo for America, was first shown in New York’s Times Square in 1987, and was remounted there in 2014. This summer, it will flash above London’s Piccadilly Circus, courtesy of the South London Gallery, as part of its exhibition of contemporary Latin American art called Under the Same Sun.

Jaar’s artwork was doubtless pertinent in 1987, but now this neon message is truly electric. When Jaar created the original billboard, the relationship between the US and Latin America was a bubbling political and cultural issue. Today, that issue has reached a boiling point – becoming a hot excuse for hatred and bigotry, fear and loathing – as extreme nationalism and xenophobia are injected into the nation’s bloodstream by Donald Trump. For Trump, this IS America – and he wants to build a wall to keep it that way.

Jaar’s work turns Trump’s rhetoric upside down. Who is Trump kidding? This really isn’t America. It stopped being so some time ago, and a wall won’t reverse history. What happens when his inhumane doctrines fail? Does a state that starts down a foul racist road reverse into liberalism when things don’t work out as promised – or does it accelerate towards fascism?

A Logo for America turns René Magritte’s philosophical painting This Is Not a Pipe into a political provocation. The United States is not America, because America is a continent, not a single nation. That continent contains many Americas and many kinds of Americans. Rio de Janeiro is as American as apple pie. But Jaar’s statement is true in another way. As a Chilean artist based in New York, he is part of a new melting pot of the Americas, the wondrous and inevitable convergence of Spanish- and Portuguese-speaking America with Anglophone US, which cannot be reversed within any decent parameters of democratic government.

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More than 17% of the US population identifies as Hispanic or Latino. Spanish is the country’s second most-spoken language. This creates rich and complex cultural connections between the country that calls itself America and the American continent it is part of. It is not outrageous for Jaar to point out the fiction that America means just the US. What is shocking is Trump’s declaration of war on the rest of the continent.

Liberals – and sane conservatives, for that matter – are still reeling from the monstrosity of Trump’s plan to build a wall between the US and Mexico. The truly frightening detail of his published plans is his policy of “compelling Mexico to pay for the wall”, a highly aggressive idea to blackmail Mexico into funding the venture. This does not resemble a reasonable democratic process; it is a series of ultimatums and deadlines. No one who has studied any history can fail to recognise the similarity to the kinds of ultimatums Germany issued in the 1930s.

The United States is a big, generous country with lots to be proud of, and hospitality is its greatest virtue of all. Can the “America” that has engraved under its Statue of Liberty “give me your tired, your poor, your huddled masses yearning to breathe free” really elect Trump as president? That is not America.